Signs of Exotic ‘Quantum Spin Liquid’ Observed in Unexpected Material

The perovskite-related metal oxide TbInO₃ exhibits an exotic state of matter called quantum spin liquid, according to a team of researchers from the University of Liverpool and McMaster University.

Due to the local terbium environment in TbInO₃, a honeycomb lattice of terbium spins emerges in the crystal structure upon cooling. Image credit: Clark et al, doi: 10.1038/s41567-018-0407-2.

The quantum spin liquid state was theoretically proposed by the Nobel laureate Philip Anderson in 1973.

In quantum spin liquids, magnetic moments behave like a liquid and do not freeze or order even at absolute zero, giving rise to several extraordinary materials properties.

The materialization of quantum spin liquids is still widely contested. As such, the discovery and exploration of new materials that may host this state of matter are active areas of advanced materials research and have potential applications in the development of quantum computing.

Using cutting-edge experimental technologies, including inelastic neutron scattering and muon spectroscopy, University of Liverpool’s Dr. Lucy Clark and colleagues discovered that the exotic quantum state in TbInO₃ emerges from the complexity of the local environment around the magnetic ions in the material, in this case, of the rare-earth element terbium.

The discovery came as a surprise to the team as TbInO₃ is a material not expected to display such unusual magnetic behavior based on its crystal structure.

“When studying intricate quantum states of matter like the quantum spin liquid, carrying out one experiment often raises more questions than it can answer,” Dr. Clark said.

“In the case of TbInO₃, however, the physics is particularly rich, and so we were especially driven to persevere.”

“Our study shows that TbInO₃ is a fascinating magnetic material, and one most likely to have many more intriguing properties for us yet to uncover.”

“This material appears deceptively simple, with terbium spins decorating a two-dimensional, triangular architecture,” said Professor Bruce Gaulin, Director of the Brockhouse Institute for Materials Research at McMaster University.

“But with the full complement of modern experimental techniques at our disposal, the low-temperature magnetism of this structure, based on two distinct terbium environments, exhibits an altogether exotic quantum disordered state of matter — an unexpected and exciting result.”

The discovery is reported in the journal Nature Physics.

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Lucy Clark et al. Two-dimensional spin liquid behaviour in the triangular-honeycomb antiferromagnet TbInO₃. Nature Physics, published online January 21, 2019; doi: 10.1038/s41567-018-0407-2